The 1997 Megatransect data shows a different perspective
on the issue of exotic plants in North America, using the
conditions of the perennial native grasses as the main indicator.
The absence of perennial native grasses in any ecosystem, provides
areas for future exotic plant infestations.

The worst case in North America, and perhaps world-wide,
is the Central Valley of California's 99+% extinction of the original
native perennial grass understory, now infested by hundreds of
exotic species. California's weedy conditions only took 150
years or about five generations to get in the current ruined condition.
When the native grass understory is missing in other States, those
areas will be vulnerable to eventually degrade into the same conditions
as California, without active restoration of the original perennial
grass understory.

The absence of the original perennial native grass
cover, is like a big "vacancy" sign, asking for
some exotic plant or weed to fill that vacancy. Some exotic plant
or plants will eventually fill those spaces, and do not be surprised
when they do so. Or, the process of restoring the original local
native grasses could begin.

The intentional sowing of exotics helps exotic
plant infestations get established, especially when you see that
in most Western states outside of California , the percentage
of weed cover is only 1-3% (except 8% in Utah ), compared
to the intentionally-sown exotics that are covering 10-38%
of the areas surveyed.

The 1:10 ratio between weeds and intentionally-sown
exotics is a staggering difference, not known before this
Megatransect was done, could become a good reason for land managers
to ban the sowing of any exotic seeds along State highways,
on Federal lands, or in wildlands.

The original native grass cover
percentage in non-riparian areas, could be used as a measure of
resistance to future exotic infestations,
with +100 being the most resistant, and minus 200 is an ecological
vacuum for new exotics to colonize:

1 to 100 percent original perennial native grass
cover = +1 to +100 on the scale.
No original native grasses, nor any exotics present yet = minus
100
No original native grasses, but exotics planted or colonizing
= minus 200.

When ecosystems drop below about 10% native grass understory cover,
they can slowly collapse, because the whole structure of the ecosystem's
understory has been so severely weakened, any new exotic can push
over the remaining native ecosystem. You can see photos of this
happening to public lands in California at http://www.ecoseeds.com/invent.html

I am predicting that protecting Endangered native
plant species that are surrounded by exotic plants, like in
many parts of the arid West, will become an extremely difficult
task---unless hundreds of millions of dollars are invested in
inventing ways to rebuild the native ecosystem, so that the exotics
cannot start the collapse of what is left.

This 2,325 miles of megatransect data is available
for use by Federal, State or local resource management agencies,
or by environmental groups, under a license agreement.

The data covers what species of grasses were growing
in 1997 at every mile-post marker, including exotics like cheatgrass
or intentionally-sown grasses like smooth brome or crested wheatgrass.
Miles covered for each State: California: 110, Colorado: 483,
Idaho: 284, Nevada: 400, South Dakota: 77, Utah: 273, Wyoming:
670, and in Yellowstone National Park: the easternmost 28 miles.

Details of the mile-by-mile 1997 Megatransect, showing the 68
miles of US highway 93 in Nevada, from Jackpot to Well. At
the time of the survey, four miles south of the H-D Summit or
18 miles north of the town of Wells, was a pristine Great Basin
Wild Rye prairie.